Retriggerable mercury switch



1969 R. D. MALLATRATT 7 RETRIGGERABLE MERCURY SWITCH Filed Oct. 7, 1966 2 Sheets-Sheet 1 arr uovsmwr a HOUS/NG o,v"

v o/v arr o/v o/v arr ATTITUDE arr I I I I o/v MOVEMENT! 7W5 co/vmcrs r55 1- 1 an/oato No 1.76 9 uwewron RICHARD MALLATRATT AQMQWW ATTORNEY Oct. 21, 1969 R. D. MALLATRATT 3,474,203

RETRIGGE'RABLE MERCURY SWITCH Filed Oct. 7, 1966 2 Sheets-Sheet 2 F/G. l2

HGT/7 INVENTOR RICHARD MALL/"WATT "damp/WM ATTORNEY United States Patent 0 3,474,203 RETRIGGERABLE MERCURY SWITCH Richard D. Mallatratt, Montgomery County, Pa., assignor US. Cl. 200-152 9 Claims ABSTRACT OF THE DISCLOSURE A mercury switch, which has a pair of separate chambers and which can be selectively movable between on and off attitudes, is arranged to limit metering of a non-conductive fluid between the chambers in response to forward movement of the housing from one attitude to the other but not in response to reverse movement. Such metering of the non-conductive fluid introduces a predetermined delay in the transfer of a quantity of mercury from one chamber to the other in response to forward movement of the housing. Because the metering does not occur in response to reverse movement, the quantity of mercury, upon such reverse movement, is substantially instantaneously transferred from the other chamber back into the one chamber.

This invention relates to a retriggerable mercury switch element.

A conventional mercury switch element comprises a hollow housing containing a quantity of mercury that bridges a pair of contacts on the housing when it is in its on attitude, and fails to bridge the contacts when the housing is in its off attitude. In use, the element is selectively movable between the two attitudes on movement being movement from the off attitude to the on accompanied by the flow of mercury into bridging relationship with the contacts, and off movement being the reverse situation accompanied by the flow of mercury out of bridging relationship with the contacts.

It is sometimes desirable to provide for a delay between the occurrence of the off movement of the housing, and the instant the mercury flows out of bridging relationship with the contacts. An element with this cap ability is useful, for instance, in applications where the element controls a lighting circuit, and it is desired to delay extingui'shment of the light for a predetermined period of time subsequent to manual turn-off of the switch. In such applications, it is also useful to provide for no delay in the flow response of the mercury to on movement of the housing, because it is usually desirable for a light to turn-on immediately upon manual operation of a switch. An element capable of a fast make and slow brea capability is shown in Patent No. 3,250,868 issued May 10, 1966, in the name of Sidney V. Worth. The delayed flow-response of the mercury to off movement of the housing is due to the provision of a non-conductive fluid in the hollow housing that fills the portion thereof not taken-up by the mercury, and the provision of metering mean that limits the flow of fluid and hence controls the flow-response of the mercury when the attitude of the housing is changed.

One of the problems with each configuration shown in the Worth patent is that it has memory of having been turned-off when on movement occurs before the mercury flows out of bridging relationship with the contacts. As a result, a configuration of the type described will generate a delay time in response to off movement that will be shorter than the desired delay by an amount of time related to time required by the switch element to recover from the effect of a previous off movement. It would be highly desirable, however, for the switch to be 3,474,203 Patented Oct. 21, 1969 "ice capable of generating the same delay each time off movement occurs. A switch having this attribute is termed retriggerable in this disclosure, and the design of a simple and reliable switch of this nature is the problem to which the present invention is directed.

Briefly, the invention involve providing an on chamber connected to the contacts such that mercury in the on chamber bridges the contacts, an off chamber that is disconnected from the contacts but is connected to the on chamber by a main conduit through which the mercury can flow, and a pair of by-pass conduits through which only the non-conductive fluid can flow. A constriction is provided in the main by-pass conduit to meter the flow of fluid, while the other or secondary by-pass directly connects the two chambers. The entrance of the secondary by-pass to the off chamber is never blocked by the mercury regardless of whether the housing is in its on or o attitude, or is moved therebetween. On the other hand, the entrance of the secondary by-pass to the on chamber is blocked by the mercury only upon initial movement of the housing to its off attitude. With this arrangement, the two chambers are freely interconnected by the secondary by-pass, when the housing is in its off attitude, and when on movement occurs. With the housing in its on attitude, mercury in the off chamber rapidly flows in response to such movement to the on chamber through the main conduit, the fluid in the on chamber that is displaced by the mercury flowing through the secondary by-pass into the off chamber. Where, however, off movement returns the housing to its off attitude, the initial 0 movement causes the mercury in the on chamber to cover the entrance of the secondary by-pass and as a consequence the fluid must flow through the constriction in the main by-pass in order to permit mercury to be displaced into the off chamber. This condition prevails until sufficient mercury is displaced from the on chamber to uncover the entrance to the secondary by-pass, at which time, the two chambers are in direct communication and the remaining mercury rapidly returns to the off chamber effective a rapid unbridging of the contacts.

The more important features of this invention have thus been outlined rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims to be granted herein shall be of sufficient breadth to prevent the appropriation of this invention by those skilled in the art.

In the drawings:

FIG. 1 is a time-plot that illustrates the retriggerable aspect of the present invention;

FIGS. 2, 3, and 4 are sectional views of the first embodiment of the invention showing off, on, and the off attitudes, respectively, of one embodiment of mercury switch element made in accordance with the present invention;

FIGS. 5 through 12 are different views of the second embodiment of a switch element. FIGS. 5 and 7 are opposite end views of the disc shown in section in FIG. 6 but with the metal end contacts removed, showing the switch element in its off attitude; FIGS. 8 and 10 are opposite end views of the disc shown in section in FIG. 9 (with the metal end contacts removed) showing the switch element after it has been moved to its on attitude; and

FIGS. 11 and 12 are opposite end views of the disc (with the metal end contacts removed) as they would appear immediately after off movement of the switch element occurs.

FIGS. 13 through 20 are different views of still a third embodiment of a switch element. FIGS. 13 and 14 are opposite end views of the disc shown in section in FIG. 14 with the metal end contact removed, and showing the switch element in its off attitude; FIGS. 16 and 18 are opposite end views of the disc shown in section in FIG. 17 with the metal end contacts removed and the switch element shown in its on position; and FIGS. 19 and 20 are opposite end views of the disc as they would appear immediately after off movement of the element occurs.

Referring now to the time-plot of FIG. 1, it can be seen that when the contacts of a switch element are bridged, as shown in the left-most portion of the lower time-plot, the switch will be on and the housing will be in its on attitude. When off movement occurs, the housin-gis moved to its ofi attitude. However, the contact remain bridged for a period of time following off movement, designated 6. When on movement of the housing accurs, subsequently, the attitude is changed from off to on, and the contacts are immediately bridged. The next off movement of the housing would normally be followed by unbridging of the contacts a period of time 6 following such off movement. However, as shown in FIG. 1, a subsequent on" movement occurring within the time interval 6 causes the contacts to remain bridged. Even though the next off movement occurs immediately after the previous on movement occurred, a retriggerable element has no memory of the previous off movement, with a result that the contacts remain bridged for a period of time 8 following the last off movement of the housing. In other words, the shortest possible delay following an off movement of the housing is equal to 5. Stated otherwise, the switch is capable of generating the delay time 6, each time off movement of the housing occurs, regardless of when this movement occurs relative to on movement.

Referring now to FIG. 2, reference numeral 10 designates the first embodiment of the switch element. Element 10 comprises a housing in the form of a cylindrical glass tube 11 that is closed at its forward axial end 12 by a tubulation connection, and at its rear axial end by base 13 in which is sealed a pair of contacts 14 and 15. Intermediate the sealed axial ends 12 and 13 of tube 11, is a fluid-porous member 16 that divides the interior of tube 11 into off chamber 17 at axial end 12, and on chamber 18 at axial end 13. Fluid-porous member 16 of a frit material formed by a sintering process, for example, such that a fluid permeable mass is defined.

Member 16 is provided with an axially extending main conduit 19 that is positioned adjacent one cylindrical wall of the tube 11. Conduit 19 provides an interconnection between chambers 17 and 18, large enough to effect the flow of mercury 20 from chamber 17 to chamber 18 when on movement of the housing occurs. The remainder of the interior of tube 11 not taken up by mercury 20 and member 16 is filled with a pressurized non-conductive fluid such as hydrogen.

The internal diameter of tube 11 constitutes a main by-pass conduit, and member 16 constitutes a delay means in such main conduit. Member 16 is also provided with a longitudinally extending cylindrical opening 21 that interconnects chambers 17 and 18. As can be seen from inspection of FIG. 2, conduit 21 freely interconnects chambers 17 and 18. When on movement of housing 11 occurs, the housing is moved from the attitude shown in FIG. 2 to the attitude shown in FIG. 3; and the non-conductive fluid in chamber 18 is displaced by the flow of mercury 20 thereinto, and passes directly through conduit 21 into chamber 17 thus permitting substantially instantaneous transfer of mercury from chamber 17 to chamber 18. As a consequence, the bridging of contacts 14 and 15 occurs substantially instantaneous with on movement.

When off movement of the housing occurs next, the mercury now contained in chamber 18 will block the entrance of conduit 21 to chamber 18 as shown in FIG. 4 and contacts 14 and 15 will remain bridged. Small slugs of mercury will then pass through main conduit 19 as the non-conductive fluid contained in chamber 17 percolates slowly through fluid-porous member 16 into chamber 18. After a period of time dependent upon the density of the material of member 16, its volume, etc., the level of mercury in chamber 18 will decrease below the entrance of conduit 21 to chamber 18 thus uncovering such entrance. At this instant there will be a direct connection between chambers 17 and 18, and the reminder of the mercury in chamber 18 will flow immediately through main conduit 19 to chamber 17 causing the contacts to be unbridged at that instant.

Both entrances of conduit 21 are too small to permit mercury to enter the conduit; and as can be seen from inspecting FIGS. 2, 3, and 4, the entrance of conduit 21 to chamber 17 is never blocked by mercury 20, regardless of the attitude of the housing. The entrance of conduit 21 to chamber 18, however, can be blocked by the mercury but only upon initial 01f movement of the housing to its off attitude as shown in FIG. 4. As a consequence of this arrangement, member 16 is effective to meter the flow of non-conductive fluid between the chambers and thus control the flow of mercury. It should also be noted that this arrangement permits the switch element '10 to be retriggerable, and perform in the manner illustrated in the time diagram shown in FIG. 1.

Referring now to FIGS. 5 through 12, switch element 30 is shown as the second embodiment of the invention. Element 30 comprises a housing in the form of a mom conductive disc 31 of ceramic material or the like, sandwiched between a pair of metallic discs 32 and 33 which constitute the contacts of this embodiment. In FIGS. 5, 6, and 7, the housing is shown in the 011" attitude, and FIGS. 5 and 7 show opposite axial end faces of the disc when the housing is in this attitude. The face of disc 31 adjacent metal disc 32 is provided with circular groove 34 that extends substantially half-way around the circumference of the disc. The axial end face of disc 31 adjacent metallic disc 33 is provided with groove 35 that extends approximately one-quarter of the circumference of the disc, and only slightly overlies the groove 34. Where the grooves 34 and 35 overlie each other, an axial extending hole 36 constituting the main by-pass conduit connects the two grooves. Rigidly connected in hole 36 is fluid-permeable material 37 that meters the flow of nonconductive fluid between the two grooves 34 and 35 when the attitude of the housing is changed. The end of grooves 34 and 35 that do not overlap are connected by means of main conduit 38 that serves to effect the exchange of mercury 39 between grooves 34 and 35. Laterally extending hole 40 is the secondary by-pass conduit that connects the two grooves 34, 35. The remainder of the space defined by grooves 34 and 35 not taken up by the mercury is filled with a pressurized non-conductive fluid, such as hydrogen for example. When the switch element is in the attitude shown in FIGS. 5, 6, and 7, the contacts 32, 33 are not bridged by mercury 39, since all of the mercury has collected in off chamber 34. When on movement of the housing occurs, it is rotated to its on attitude, and the main conduit 38 is substantially horizontal permitting the mercury 39 contained in groove 34 to flow through the conduit into groove 35 as shown in FIGS. 8 and 10. The flow-response of the mercury is substantially simultaneous with on movement of the housing because of the presence of secondary by-pass conduit 40 which directly connects groove 34 to groove 35 and permits the fluid displaced from groove 35 by the flow of mercury thereinto, to flow directly into groove 34. In this attitude, contacts 32 and 33 are bridged by the mercury contained in groove 34 and groove 35, and the mercury contained in main conduit 38.

When the housing is moved to its off attitude as shown in FIGS. 11 and 12, the initial oft movement of the housing causes the mercury globual in groove 35 to close the entrance of secondary by'-pass 40 to groove 35. This prevents a rapid transfer of mercury in groove 35 back into groove 34 because the fluid trapped in groove 34 can enter groove 35, as the mercury is displaced from groove 35 to groove 34, only by passing through delay means 37. Eventually suflicient fluid is displaced, and the level of mercury contained in groove 35 drops to a point which the entrance of secondary-.-by-pass 40 to groove 35 is uncovered permitting grooves 34 and 35 to be freely interconnected once more. At such time, the remainder of the mercury in groove 34 suddenly passes through main conduit 38 into groove 34 as shown in the drawings, and the contacts are unbridged. From the above description it can be seen that embodiment 30 operates in the same manner as embodiment 10, in that each embodiment constitutes a retriggerable mercury switch element.

Still another embodiment of the invention in FIGS. 13 through 20 to which reference is now made. Switch element 50 is similar in nature to element 30 already described. That is to say element 50 comprises a housing in the form of a non-conducting disc 51 sandwiched in between a pair of metallic contacts 52 and 53. In this embodiment, however, the off chamber constituted by a blind segmented groove 54 in the end face of disc 51 that is adjacent to contact 53. The on chamber is constituted by a segmented hole 55 that passes from one face of the disc to the other, thus interconnecting the two contacts 52, 53. At one end of each of the chamber's 54 and 55 adjacent the respective end faces of the disc, there is a groove of reduced depth such that the groove of reduced depth in each face overlie each other. Main by-pass conduit 56 connects the two portions of re duced depth and contains delay means 57 in the form of a fluid permeable member. Main conduit 58 connects the chambers 54 and 55 at adjacent ends and serves to effect the exchange of mercury 6.0 between the cham bers. Secondary by-pass conduit 59 also connects to the chambers 54 and 55 as shown in the drawing. The remainder of the space defined by chambers 54 and 55 and not taken up by the mercury, is filled with a pressurized non-conductive fluid such as hydrogen for example.

When element 50 is in the position shown in FIGS. l3, l4, and 15, namely the off attitude, all of the mercury 60 is contained within the off chamber 54. Rotation of element 50 to its on attitude will cause the mercury contained in chamber 54 to flow through main conduit 58 into chamber 55 thereby permitting the contacts 52, 53 to be bridged since chamber 55 is open at each axial end to contacts 52 and '53. The flow of mercury through conduit 58 occurs substantially simultaneous with the on movement of the housing because secondary by-pass conduit '59 directly connects chambers 54 and 55, thus permitting the fluid contained in chamber 55 and displaced by the flow of mercury thereinto, to pass immediately into chamber 54. This condition of the element is illustrated in FIGS. 16, 17, and 18.

Contacts 52 and 53 are unbridged when the mercury drains from the on chamber 55 back into the off chamber 54. Draining of chamber 55 occurs subsequently to rotation of the housing to its off attitude. Initial 01f movement of the housing causes the mercury contained in chamber 55 to block the entrance of secondary by-pass conduit 59 to chamber 55. Consequently, mercury cannot flow rapidly from chamber 55 through conduit 58 into chamber 54, since the hydrogen displaced in 54 must pass through delay means 57 in order to enter chamber 55. As a consequence of this, the mercury contained in chamber 55 slowly drains through conduit 58 until the level of the mercury remaining in chamber 6 55 falls below the entrance of secondary by-pass conduit 59 to chamber 55. At such time, the chambers 54 and 55 are connected together through open by-pass conduit 59, and the remaining mercury in chamber 55 rapidly is transferred into chamber 58 thereby unbridging contacts 52 and 53.

In this embodiment also, it can be seen that on movement of the housing at any instant before the mercury in chamber 55 uncovers the entrance of conduit 59 to chamber 55, will cause the remainder of the mercury contained in chamber 54 to be immediately transferred back into chamber 55. This occurs because the entrances of conduit 59 to chambers 54 and 55 are uncovered when such on movement occurs. This has the effect of immediately constituting the mercury in chamber 55 in the same state that it occupied the previous time the housing was moved to on position. In other words, the switch element exhibits no memory of its off attitude. Thus, switch element 50 is retriggerable and will perform in the same manner as indicated in the time diagram shown in FIG. 1.

While the single main by-pass as shown in the drawing and described above is capable of effecting the transfer of mercury from the off chamber to the on chamber substantially simultaneously with on movement of the housing, it should be understood that multiple conduits could functionally achieve the result of the single main by-pass. In addition, it should also be understood that a delayed response to on movement could be incorporated into each of the above embodiments by the insertion of a fluid-permeable mass in the main by pass. The latter arrangement would permit a slow make as well as a slow break switch configuration.

What is claimed is:

1. A movable mercury switch element comprising:

(a) a hollow housing divided into a first chamber separated from a second chamber and containing mercury partially filling the housing and a non-conductive fluid in the remainder of the housing;

(b) electrical contacts associated with one of said chambers;

(c) said housing being positionable in an on reference attitude in which a quantity of said mercury bridges said contacts and an off reference attitude in which said quantity of mercury fails to bridge said contacts, and selectively movable between the two reference attitudes; and

((1) housing means associated with said housing for metering the flow of said non-conductive fluid between the chambers in response to movement of the housing from only one of the two attitudes to the other of the two attitudes to introduce a predetermined delay in the transfer of said quantity of mercury from the first chamber to the second chamber in response to movement of the housing from said one attitude to said other attitude and to cause said quantity of mercury to be substantially instantaneously transferred from the second chamber back to the first chamber in response to movement of the housing from said other attitude to said one attitude.

2. The element of claim 1 wherein a dividing member divides said housing into said first and second separate chambers and includes:

(a) a main conduit interconnecting the chambers for effecting the transfer of mercury therebetween;

(b) a secondary by-pass conduit interconnecting the chambers for effecting the transfer therebetween of only the non-conductive fluid;

(c) fluid porous means interconnecting the chambers for metering the non-conductive fluid between the chambers; and

(d) the entrance of the secondary by-pass conduit to the second chamber being unblocked by said quantity of mercury whenever the housing is in either of its two reference attitudes or moved therebetween, and the entrance of the secondary by-pass conduit to the first chamber being blocked by said quantity of mercury upon initial movement of the housing from its one attitude to its other attitude for causing the non-conductive fluid t flow from the second chamber to the first chamber through said fluid porous means until sufiicient of said quantity of mercury flows from the first to the second chamber through the main conduit and unblocks the entrance of the secondary by-pass conduit to the first chamber.

3. The element of claim 2 wherein said housing is in the form of a cylindrical tube that is closed at its opposite axial ends and said dividing member is between said axial ends whereby said first chamber is adjacent one axial end and said second chamber is adjacent the other axial end, and said main conduit is eccentrically located relative to the axis of said tube.

4. The element of claim 3 wherein the dividing member is itself fluid porous.

5. The element of claim 3 wherein said contacts are associated with said first chamber whereby said contacts are bridged by said quantity of mercury when said housing is in said one attitude.

6. The element of claim 3 wherein at least one of said contacts is axially directed and has a free end terminating in the interior of the chamber with which the contacts are associated, said free end being angularly directed toward said main conduit.

7. The element of claim 3 wherein the dividing memher is a non-metallic disc establishing said first and second chambers, said disc having a main conduit therein interconnecting said chambers for effecting the transfer of mercury therebetween, and a pair of by-pass conduits therein interconnecting said chambers for effecting the transfer of said non-conducting fluid therebetween, one of said by-pass conduits containing fluid permeable means.

8. The element of claim 7, wherein said non-metallic disc has opposite axial faces and said contacts are in the form of metallic discs, one attached to each of said axial faces, said first and second chambers being defined by circular-shaped grooves in each axial face of said nonmetallic disc.

9. The element of claim 8 wherein one of said chambers is defined by a groove that interconnects the axial faces of said non-metallic disc.

References Cited UNITED STATES PATENTS 2,206,436 7/1940 Spencer ZOO-33.1 2,800,537 7/1957 Hesh 20033.1 2,119,022 5/1938 Murad 20033.1 X 2,254,710 9/1941 Reid 200l52 X 2,392,829 1/1946 Allison ZOO-33.1 2,972,025 2/ 1961 Banks 20033.1

ROBERT K. SCHAEFER, Primary Examiner H. J. HOHAUSER, Assistant Examiner US. Cl. X.R.

ZOO-33.1 

